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A. .M. WELLINGTON, Decd. I

' A B WELLINGTON Execumx ART OF AND APPARATUS FOR CONVERTING HEAT INTO WORK BY AGENCY 0F VAPOR PRESSURE.

Patented Nov. 19, 1895.

WITNESSES.

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ART OF AND APPARATUS FOR CONVERTING HEAT INTO WORK BY IN VE N TOR WITNESSES ATTDRNE Y5.-

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A B WELLINGTON, Executrix. ART OF AND APPARATUS FOR CONVERTING HBAT'INTO WORKBY AGENCY 0F VAPOR PRESSURE.

N -54%,981j Paten tedwwi C OOODOOODD L 00 L INVENTOH e w w A TTOHNEKS ANDREW B GRAHAM. PHOTO-UTNQWASHINGTOILD C.

UNITED STATES PATENT om n.

ARTHUR M. WELLINGTON,OF NEWYVORK, N. Y.; AGNES BATEsjwELLINo- TON EXEoUrEIX or SAID ARTHUR M. WELLINGTON, DECEASED.

ART OF AND APPARATUSFOR CONVERTING HEAI INTO WORK BY AGENCY F VAPOR PRESSURE.

SPECIFICATION forming part of Letters Patent No. 549,981, dated November 19, 1895. Application filed February 8, 1894. Renewed April 20, 1895. Serial No. 6,530. (N0 model.)

To all whom it may concern:

Be it known that I, ARTHUR MELLEN WEL- LINGTON, a citizen of the United States, residing at New York, county of New York, and State of New York, have invented certain new and useful Improvements in the Art of Oonvertin g Heat into Work by the Agency of Vapor Pressure and Apparatus for the Same, fully described and represented in the following specification and the accompanying drawings, forming a part of the same.

The basic element of my new process lies in the dissociation of the fire or other irregular source of heat from the boiler or other pressure-generator containing the confined working substance, in order that the eflective connection between the two may be secured by a heat conveying substance which is passed from the source of heat to the pressure-generator, and which in the typical case and except for special reasons is returned to the source of heat to be reheated, so as to move in a closed cycle, being alternately heated to a desired or convenient point, passed to the pressure generator containing the working substance, cooled to a desired or convenient point by the surrender of heat to the working substance, and returned directly or indirectly to the source of heat to be reheated. In special cases the heat-carrying substance is not returned to be reheated, but worked in open cycle, a new mass being continually received, heated, cooled, and discharged.

The heat-conveying substance I call, for convenience, the circulating fluid, whether it be worked in closed or open cycle. It is preferably a liquid, but may be solid or gaseous in part or Whole, and its sole function as a part of this process is to flow around in passageways which are usually endless, being preferably in continuous motion and under more or less careful regulation as to speed and temperature, and thus to convey heat to the working substance. Having such a hot fluid in motion, however, it may at times be convenient to take some heat from it for some other use, and certain gains to this process may at times result from doing so. The circulating fluid may consist either of one or of several different heat conveying substances circulated either as a common mass or, as is often expedient for practical reasons, in two or more distinct sets of passage-ways, but in either case it is spoken of collectively as the circulating fluid.

Among the cases in which it is inexpedient to use over and over a single mass of circulating fluid these two are prominent: First, in certain applications of my process a surrounding mass of air or water already heated or partially heated to the desired point by nature or in the practice of some other art may be drawn upon for the circulating fluid, and there is then an obvious practical advantage in receiving a fresh mass of circulating fluid from this existing supply instead of using a single mass over and over in closed cycle. Secondly, in all cases when fire is used for heat a continuous supply of fresh air must be taken into the heater to support combustion, and the gas thus used may most advantageously be made a part of the circulating fluid by first causing it to absorb as much as possible of otherwise rejected Waste heat on its way to the heater, and then, after it has supported combustion, arranging to insure its reduction to an admissible temperature and passing it through the pressure-generator as a part of the circulating fluid, in order that it may surrender further heat before discharge. With care to insure that this gas shall be cooled down to a reasonably uniform and moderate temperature before such use, it not only may be but in large plants should be used as a part of the circulating fluid, and if so used it must be used in open cycle, even though the rest of the circulating fluid is used in closed cycle. It will be understood, therefore, that the term circulating fluid is intended to cover not only a fluid a single mass of which is used repeatedly, but also a fluid which is drawn from a supply utilized in transporting heat to the working substance and then voided from the mechanism.

As between air and water as a circulating fluid, each has decided theoretical advantages. Air has the very great advantage of not being changed in physical properties by any extremes of temperature, and also of being a supporter of combustion, so that when air is used as the circulating fluid the heater may be a closed chamber in which fuel is burned in the circulating fluid itself at a regular rate, such as just to supply the heat needed to raise it to the required temperature, with a resulting large economy of fuel, which in the best applications of the process may even rise to perfect economy of combustion, the gases being discharged no hotter than when received. Being eight hundred and fifteen times lighter than water, the same propelling pressure will drive it about V815 8.55 times as fast, and the friction loss will be still less in proportion, thus in a measure compensating for its lack of mass and low specific heat. For the opposite ex-. tremes of small engines, forwhich simplicity is an object and high economy relatively unimportant,and large engines working through a very great thermal range in order to realize high economy, air alone may be a very suitable circulating medium. Air has the further great advantage in certain special applications of the process that it may be caused to change in temperature without any direct application of heat or cold simply by changin g its status as compressed or uncompressed. Such special applications are covered by separate applications, however, and need not be described herein. On the other hand, as a heat-transmitter, air is extremely inefficient. A given heating-surface is from thirty to one hundred times as efficient between water and water and steam as between air and water or steam. Therefore a correspondingly great excess of heating surface, or else of thermal head, or difference between the temperatures of the heating and the heated substances, is required if the air be used over what is required with water as a circulating fluid. \Vater has the great advantage of a higher specific heat than any other known body, and my experiments indicate that it has also, notably, greater powers of imparting heat to metallic surfaces than any other convenientlyavailable fluid, but it has the great disadvantage of being liquid at atmospheric pressures only between zero and 100 centigrade. To overcome this deficiency by increasing the thermal range within which water is liquid, it maybe circulated under pressure, and this will often be expedient, though it involves certain inconveniences even when the water is used in a closed cycle and still more in open cycle. As a leading motive for using water rather than some other liquid will often be to use it in open cycle, water is not an entirely desirable circulating fluid and may rarely be useful for this end at all except when its boiling-point is artificially raised by circulating it under pressure. In special applications of the process water in the form of steam may serve as circulating fluid, especially when it is only a small portion of the total mass, but such use is not typical nor ordinarily expedient.

If steam were to constitute a considerable fraction of the circulating fluid, the question of how that steam should be generated would then arise, and if it be generated in the ordinary way all the defects of practice which it is the purpose of this invention to correct would still be retained. The use of steam or any other vapor condensed from gaseous to liquid state in circulation as the sole or main constituent of the circulating fluid is never expedient,and is not included within the term circulating fluid. Such a vapor condensed in circulation may, however, be used as a small part of the total mass of a circulating fluid, of which the gases of combustion form a part, for the incidental purpose of producing an induced draft and to cool down the gases of combustion to a temperature approximating more closely that of the liquid circulation. other liquids, of which paraflinc-oil is an example, which remain liquid within all extremes of temperature from zero to 300 centigrade, or even more, which are chemically neutral and stable, even if subjected to longcontinued alternations of these temperatures, which do not gum and which may be circulated with evenless friction than water. They have in general a specific heat of about 0.4, which means that they must be circulated about two and one-half times as fast to supply the same quantity of heat per hour to the same surfaces, and I have found them to have considerably less heat-transmittin g efficiency than water when in contact with heating-surfaces; but the lower specific heat is an advantage, as it enables the fluid to be circulated faster than it otherwise could. The speed at best is slow, and 011 the whole these oils have most of the advantages of water, with some peculiarly their own, and they constitute a convenient and suitable circulating medium when a liquid is used in a closed cycle, though requiring much more heatingsurface for equal efficiency. \Vhen so used in closed cycle, the scarcity or cost of the liquid does not matter, nor even its noxiousness in a free state, since no great quantity is used and there is little or no waste. There is therefore a wide range of choice in regard to the components of the cireulatin g fluid; but, so far as I yet know, either water or air or purified paraffin e-oil combine the most advan tages, except as follows:

As above stated, the circulating fluid may be solid in part or whole. An exclusivelysolid circulation in the form of a movable solid mass is a mere possibility; but it is ratherthe rule than the exception that a combination of solid liquid and gaseous elements gives a better circulating fluid than either one or two such elements alone. \Vhether the base of the circulating fluid be liquid (except possibly in the case of water) or gaseous, there is generally a decided advantage in mixing with it mechanically some pulverized carbonaceous or other substances of good radiating properties, while for certain extremes of both heat and cold which some of the best applications of this process require There are, however, a variety of no liquid known to me has the requisite physi-v fluid may be any gaseous or liquid substance to which heat may be applied while it is confined within a chamber, with the effect of generating or increasing therein, a vaporpressure which enables the confined substance to do useful work.

In this specification and the claims all gases are considered as the vapors of liquids, whether ordinarily condensable or not. Then used in connection with an engine for producin g motion, the term working substance refers only to the substance which by its expansive pressure causes the motion, but when used more broadly and without special reference to the mechanism in which the working substance is used, the work to which the term is intended to refer includes any sort of useful work which may be done by vaporpressure generated or increased by heat, whether it be working a mechanical engine or securing any other result by the surrender of part or of all of its heat or pressure.

The dissociation of the source of heat and working substance is simply a thermal dissociation, which may or may not be mechanical also. Ordinarily, two parts which are intended to be thermally dissociated should not be mechanically contiguous, but mechanical convenience may often render this expedient,even at some slight sacrifice of thermal dissociation. Whenever the source of heat and the working substance are so disposed that the circulating fluid may serve as the effective thermal connection between them, to the exclusion of interference by unregulated heat with the moderate and controllable action of the circulating fluid so far as is practical, the source of heat and working substance are thermally dissociated within the meaning of the term as used herein, although there may be some considerable residue of direct action of the one upon the other by conduction of heat through common metallic parts or otherwise.

By the apparently simple change of process above outlined we attain, or may attain, a number of highly important ends. We eliminate all temperature strains from the presslire-generator by subjecting it only to a regulated and uniform heat. l/Ve may multiply many times the efficiency of the heating-surfaces when the circulating fluid is a liquid by securing liquid instead of gaseous contact with the heating-surfaces. More important than all else,perhaps,we may radically modify for the better the functional action of the pressure-generator by applying our greatest heat at the top of the pressure-generator instead of the bottom and carrying the heating and the heated substance in opposing currents past each other, the heating substance descending as it cools, while the heated substance-rises as it grows hotter,thus producing differential temperatures within the boiler, all

its materials and contents being at all times hottest at the top, coldest at the bottom,by necessary efiect of the functional action, whereas in every boiler to which fire is applied directly there exists a'reverse and injurious tendency and status. With a circulating fluid, also, we may permeate the entire interior of the pressure-generator with our heat-supply, the steam-space as well as the water-space. The effect of these changes in practice and in the status of the pressure generator is too im portant and far-reaching to be explained in few words or to be at once comprehended. When followed out to its legitimate results it is found to be revolutionary, both as to the theory and the practice of both steam making and steam using. The effect upon steamboiler practice is such that the boiler practically vanishes asa factor in the bulk and cost of steam-engines, and may more accurately be conceived of as a mere enlargement of the steam-pipe in which a liquid changes into gas as it moves along. The effect upon the theory of steam-generation is to establish broadly as a general theorem that the irregular application of heat in bulk, and especially the unregulated heat of fire, to vaporizing working substance under pressure is an error of process which is destructive of economy. The effect upon the use of steam is to'make possible complete new processes for the conversion of heat into work with a percentage of economy heretofore unattainable, as shown more fully in this and other applications.

This present application covers especially the improvements attained by the application of the new process of steam-generation in connection with present known processes of utilizing vapor pressure by changes based on a recognition of the fact stated above that the irregular application of heat in bulk, and especially the direct heat of fire to a confined working substance under pressure is an error of process which is destructive of economy.

Vhile my improved process is of general application to all, known types of air or vapor heat-engines, and to most other mechanisms in which heat is caused to do useful work by the generation and application of vapor pressure, it is best used, perhaps, in connection with various forms of steam-engines. The invention will, therefore, be described and illustrated with special application to steam-generation, reference being had to the accompanying drawings, forming a part of this specification, in which are illustrated diagrammatically the general features and methods of application of my process and an apparatus which I have found to be well suited for carrying out the process, the general combinations and certain specific features of which apparatus form in themselves parts of the invention.

In the drawings, Figure 1 is a dragram illustrative of the general process. Figs. 2 to 7 are diagrams illustrating various methods of applying the process. Fig. 8 is a diagram showing in outline the general system of normal or useful and abnormal or wasteful circulation, the abnormal being shown in dot-ted lines and the normal with two boilers and one condenser in circuit. Fig. 9 isa drawing, also largely diagrammatic, of a substantially complete apparatus embodying the circulatory system and its adjuncts in their complete form but in the simplest caseviz., with only one boiler and no condenser in circuit, but provided with a condenser out of circuit. Fig. 10 is a detail of the expansion and supply tank constructions. Figs. 11, 12, and 13 are details of the boiler. Fig. 1i is a detail of the feeding and regulating attachments of the boiler. Fig. 15 is a detail of the valve controlling the boiler-supply. Fig. 16 isa diagrammatic vertical section of the non-circuit evaporative condenser. Fig. 17 is a detail of the grate-shaker connections. Fig. 18 is a sectional detail of the circulating-pump.

Stated broadly as a general principle applicable generally to existing processes utilizing vapor-pressure, the nature of the alleged error of process above referred to, and the correction of which forms the basis of this specification, may be explained thus: Fire in large mass is an uncontrollable thing. Fluctuations of 1,000 centigrade (1,800 Fahrenheit) or more may occur locally in a furnace within a few minutes or seconds of each other, and even greater fluctuations occur in the furnace as a whole at longer yet frequent intervals. This exposes all the containing-surfaces to intense and irregular alternations of extreme heat and cold. Hence the first necessity for reasonable lightness and durability is that these surfaces should be free to expand and contract ad Zibizum without doing harm. To use the other side of the same surfaces as the containingsurfaces for a mass of an explosive substance under pressure, but which yet by its conditions has a constant temperature, is illogical and absurd. It is yoking together two discordant and antagonistic things,which may possiblybe done with safety, but only with costly precautions and occasional failures. These two uses of the same chamber are antagonistic and naturally require dissociation. The firechamber needs only the passive resistance of fire-brick, but no great strength. The steam and water chamber, if the heating as well as the heated fluid may be at sensibly constant and controlled temperatures, needs only static strength and no massiveness at all; but, on the contrary, its function demands all possible thinness and delicacy of surfaces that static strength permits. This first false step once takenof making one what should be two there is no resource remaining but to take several other false steps to avoid the consequences of the first. To resist the temperature strains alone, we are compelled to make the surfaces objectionably thick for heat-transmitting purposes. The direct action of fire upon them soon gives them also a non-conducting scale or coating, which alone decreases by one-half to four-fifths their heat-transmitting capacity. \Vorse than all, the fierce heat impacts make it absolutely necessary that all surfaces to which they are applied shall be well immersed in water, which in turn requires that the most intense heat shall be applied at or near the bottom of the boiler and of the contained mass of liquid and shall decrease in intensity toward the top, whereas the best evaporative conditions require that it shall increase toward the top. This error in the point of applying the most intense heat in its turn insures that nearly all the steam shall be generated at the bottom of the liquid instead of at the top, and hence that it must rise through the entire mass of liquid to escape from it. Thus arises a necessity for a violent circulation, in order that fresh liquid may be continually flowing in from the side to replace that which is continually removed and carried upward from the most heated surfaces, not so much by evaporation as by the mechanical action of the rising steam. This in turn makes it absolutely necessary that there shall be within a large mass of rapidly-circulating working substance to serve as an equalizer and harmless receiver of these heat-impacts and to furnish a sufficient mass, not only to give a considerable depth of water over the heated surfaces, but also to fill certain otherwise inert side spaces for the downward circulation to which from the nature of their function heat must not be applied, and which,therefore,only serve to increase the bulk of the boiler and workin g substance without adding to the evaporation. It is true that the large mass of contained working substance thus enforced has the slight additional use of giving a small store of reserve power which may be drawn on for a few moments; but that function, also, is better subserved otherwise. This large quantity of functionally useless and inactive working substance makes the boiler a magazine of explosive energy and so necessitates still greater strength, not for ordinary needs, but for rare emergencies,which exist only because of the uncontrolled and intense heat-impacts. Under my process, when best applied, I rarely need so much as one per cent. of the usual mass of working substance. This need for rapid circulation of a great mass of liquid in its turn requires that the active heating-surfaces shall be widely spaced with large free intervals between them for circulation, and this in its turn, with the requirement that all parts shall be of massive strength, forbids the production of any large amount of heatingsurface in a small space, and hence requires that what heating-surface there is shall be intensely active and the ebullition from it intense and violent. This in its turn demands that the external thermal head shall be large, and hence that much heat shall be discharged to waste, and also insures internally such violent upward foaming from the most heated spots that a large amount of priming must result, and this last in its turn requires a large and otherwise useless steam space above the seething water, in order that in its comparative quiet some of this water may drop back again out of the steam. Naturally much of it refuses to drop'back, but remains in the steam. Again, the intense and irregular heats used forbid our exposing this steam to furtherheating-surface to evaporate its entrained water and superheat the steam. The gases must be discharged to waste still highly heated for the very reason that they are so highly and irregularly heated, while the steam cools in its steam-space rather than is heated, that being the coldest part of the boiler, whereas it should be the hottest. Again, returning to the fire, in order that the concentrated impacts of heat may not be absolutely destructive, it is necessary to spread out the fire over a large area, fire it with great care and skill, and leave large and to a great extent otherwise needless vacant spaces above and around the fire to prevent too fierce attack by it upon the working substance, further increasing bulk and massiveness.

So I might go on and trace the calamitous effect of the basic error stated through the entire mechanism, especially in connection with the prevalent idea that water is the only convenient, or a specially convenient,working substance, which is certainly sound enough under present conditions of practice, and un der any conditions for non-condensing engines, but which has no other logical foundation for con (lensing-engines when traced back to its starting point than the basic error referred to. It is believed that, in the light of a larger knowledge and at no distant day, these methods will be looked back upon with wonder as needlessly barbaric, absurd, and crudeas much so, both in nature and degree, as the old Newcomen process of using the same chamber both as a working engine and a condenser. In fact, the modification of process covered by this application bears a close analogy to that by which the modern steam-engine process was evolved from the Newcomen or pre-Vatt process, each consisting simply in a differentiation of process by which additional steps are introduced to effect the same result. The essentials of the respective basic processes may thus be stated:

The old pre-Watt process employed three elements: first, a furnace and boiler combined; second, a passage for working substance, and, third, a working engine and condenser combined. Watt, in 17 69, ditferentiated this process by separating the engine and condenser, and thus increased the conversion efficiency of the steam from one per cent. to about five per cent., which one hundred and twenty-five years of effort in perfecting details has since expanded to a maximum efficiency of about fifteen per cent. The process thus obtained and still in universal use employs the following elements: first, a furnace and boiler combined; second, a passage for working substance; third, a working engine; fourth, a passage for the exhaust; fifth, a condenser voiding combined heat and working substance externally. In the process of forming the present invention, however, this Watt process is differentiated still further by separating the furnace and boiler, as illus trated in the diagram Fig. 1 of the drawings, accompanying this specification and employing the following seven elements: first, a heater H; second, a passage V for circulating fluid from heater to boiler, and preferably, also, for return to boiler; third, a boiler B to which no fire is applied; fourth, a passage P from boiler to engine; fifth, a working-engine E; sixth, a passage P for the exhaust; seventh, a condenser C.

It is obvious that this process, as well as the pre-Watt and Watt processes may be abbreviated at the expense of economy by omitting the condensing step. The two latter processes then become identical, each alike giving the modern non-condensing-engine process, but the pre-Watt process never was, in fact, so abbreviated.

'Before describing the details of my new process I will describe the general method of applyingit to existing forms of steam-engines and the advantages which result therefrom.

I will take the locomotive as one of the most unpromising examples of modern engines for a modification of process. I will regard and treat its two engines as one, that making the case still less favorable. Let, then, all fire be removed from the fire-box and placed in a separate receptacle, say on the tender. Let the grate be closed and made water-tight. Let suitable baffle-plates be put into the adandoned fire-box and at the ends of the tubes, so as to promote an effective circulation, and let the first and greatest heat be applied at the top of the boiler and not the bottom. Let hot paraffine-oil or hot water under pressure be circulated from the fire box through the boiler as the boilers source of heat, and by suitable regulating appliances, manual or automatic, let the oil be heated to some approximately fixed pointsay to 355 centigrade (671 Fahrenheit)and cooled before returning to the heater down to the boiler-temperature or any desired point above it. Let the enginebe working high pressure, as usual, between 100 and 185 centigrade, (212 and 365 Fahrenheit,) correspondingto steam at 11.2 and one atmosphere (one hundred and sixty-four pounds and 14.7 pounds per square inch) absolute pressure. These conditions only require that the mass per stroke of the circulating fluid shall be about 3.87 times the mass of water evaporated per stroke, (or 9. 68 times for specific heat 0.4,) implying an almost imperceptible speed of circulation. Fig. 2 of the drawings shows to a rude vertical scale of temperature the thermal conditions then obtaining, in which H is the heater on the tender and a the engine working non-condensing between T and T. The arrows show the path of the circulating fluid, which merely serves to convey heat to the steam, not to bring any exhaust heat back. At the temperature and point T the circulating fluid enters the boilers, is therein cooled through 255 eentigrade down to the steamtemperature, and then returns back to the heater to be heated up again to T. It is now easily seen. that we have thereby enormously increased the thermal cfliciency of the boiler. A liquid at 355 centigrade ((371 Fahrenheit) is in contact with every part of the fire-box and tubes, this being hotter than the most exposed points of the inner face of the firebox ever are with radiant heat at 1,500 to 2,000 centigrade (2,732 to 3,639 Fahrenheit) acting directly upon them, as shown by the fact that lead safety-plu s melting considerably below 355 centigrade (671 Fahrenheit) do not melt in it; but every part of the heating-surface, both fire-box and tubes, now is or may be exposed to this same temperature and liquid contact. As illustrated in Fig. 2, the mean thermal head for the whole heating-surface is only half as great as this; but as hot water or oil is from twenty to fifty times as effective a heating medium as air with agiven surface and a given transmission interval we have then an enormous surplus of heating-power. Our greatest heat being applied at the top, our greatest steam-generation is there, and there is no longer either necessity for or tendency to interior circulation; but our metal surfaces may now be bright instead of dull, again greatly increasing their heattransmitting capacity \Ve may also run heating tubes through our steam-space, and thus not only dry, but highly snperheat our steam. \Ve have no longer anysensible temperature st *ains. \Ve can dispense with nearly all of the water in the boiler, which has been put there only to receive and equalize heat impacts which no longer exist and to maintain a circulation which no longer is needed. Both for this reason and because of our enormous excess of heat supply, we can make our boiler much smaller. "0 also need no extra thickness as a guard against explosions. \Ve can also use much thinner and smaller tubes, and so reduce our boiler still smaller. \Ve need no longer any space whatever for the fire-box. The superheating of the steam alone, which is a natural result of the above process of steamgeneration, is likely to reduce greatly or even avoid altogether the customary excess of thirty to fifty per cent. in actual steam consumption over what the indicator-cards call for. Every condition is improved. Our heater on the tender also works under improved conditions. The grate and its containing-box may be smaller and the fire correspondingly deeper. It maybe contained in a plain iron box, which does not attempt to resist temperature strains and so does not deteriorate under them. The

surrounding liquid is below its boiling-point.

Consequently it generates no steam, and consequently we may use for it any kind of cheap metallic surfaces which may safely be brought quite close to the fire. The gases of combustion may be carried in close contact with these metallic surfaces and their extension for some distance at the cool end, and thus be much cooled down before discharged. The irregularities of temperature which necessarily result from using the same surfaces alternately and irregularly for heating, evaporating, and superheating,with their very different rates of heat absorption, no longer exist, while the irregular heat impacts which we cannot avoid in a fire-box do no harm to such surfaces as described, which are free to expand and contract. Our exhaust-steam may still be used to cause artificial draft; but by placinga thermostat in the circulating fluid we may regulate precisely the air-supply which we allow to enter the fire, so as to produce just enough heat and no morea method of regulation which we cannot use when the heated substance is the steam-producing liquid itself, which does not change in temperature with the quantity of heat supplied after its working pressure has once been reached.

It will now be obvious, also, that having greatly reduced the necessary size of our boiler we may move back our heater from the tender to its usual place on the engine and still preserve all the conditions with the heater on the tender. The dissociation of boiler and fire-box, as above explained, refers only to thermal conditions and does not forbid that they be mechanically contiguous. \Ve have simply to cut off the present fire-box and its heating-surface bodily, put a much smaller plain box fora heaterin its placeand we still have left, in the barrel of the boiler only, many times more steam-space and heatingsurface than we have any use for. Therefore reducing 0 ur boiler to its required dimensions only we have plenty of spare space and weight for an air-cooler or a condenser if we choose to add one. All this has been accomplished under the most unfavorable conditions, allowing for only one engine. Vith two or more engines to run we can do much better in a variety of ways, as illustrated in Figs. 3 to 7 of the drawings, and as will be explained hereinafter.

The preceding is regarded as sufficient to establish the generality of the principle that the new process as applied to steam generation by introducing a circulating fluid as the thermal connection between fire and boiler is a direct advantage to the simplest engine processes, in addition to opening an easy road to further and greater modifications of process.

I now proceed to describe the details of the process more precisely, since its advantages only have been so far explained, and not its limitations. A circulating fluid cannot be used without great sacrifice of its possible advantages, except in. connection with certain regulatory andother adjuncts so far uncon- .sidered.

In the first place, if the circulating fluid be a liquid, an expansion-tank or its equivalent must be used, since all fluids expand when heated with irresistible force, and since the circulating-pipes should at all times be full of fluid, and yet not more than full. It is then theoretically possible by providing circulating-passages of immense strength, such as can resist any extreme of vapor-pressure which any fire can create and by substituting great vigilance for automatic regulation, to circulate a heat-conveying liquid between an ordinary unregulated fire and an ordinary type of boiler and realize some of the advantages which have been described; but for practical resultsfrom the process, except, pos sibly, in special applications not forming a part of the invention covered by the present application, whether the circulating-fluid be a liquid or a gas, it must include one or more of the following features, and to realize its highest advantages it should include them all. These adjuncts are arranged in their logical sequence in the process.

A. Regulation of the maximum temperature of the circulating fluid-that, is the temperature of the circulating fluid as it passes to the boiler.

B. Regulation of the volume of the circulating fluid so as to keep it sensibly constant at all temperatures.

C. Application of the circulating fluid to the working substance in such a manner as to produce and utilize differential temperatures within the boiler, as below explained.

D. Regulation of the minimum temperature of the circulating fluidthat is, the tempcrature to which the circulating fluid is cooled in the boiler-preferably by controlling the speed of circulation.

E. Regulation of the volume of working substance in theboiler so as to keep it sensibly constant.

F. Regulation of the degree of pressure which can exist in the boiler.

Most of these adjuncts may be quite simply effected, and by different means. The appliances which, as a rule, I deem preferable are given below; but I limit myself to no particular form of these appliances, as the process may be adapted to the use of many different forms. I proceed to consider them in order.

Adjunct A.Regulaion of the lllamimum Temperature of the Circulating Fluid.

By this I mean the regulation of the temperature of the circulating fluid on the hot side-that is, as it passes to the boiler or boilerswhich is its maximum. This is the most essential element in respect to safety of the apparatus when the fluid is heated by the direct action of fire. Otherwise all the passages must be of immense strength and thickness, since the volume of the circulating fluid is small, and its capacity for absorbingheat also small, because of the lack of any vaporization. Therefore without regulation of the temperature imparted the pressure within the pipes is liable to rise at any time when rapid withdrawal of heat ceases very nearly to that due-to the temperature of combustion, which is several hundred atmospheres with any probable circulating fluid. Of course any danger of explosion from such pressure may be guarded against by a suitable safetyvalve, which in any case should be added as an additional precaution; but this involves 'loss of fluid from the circulating-pipes, and

consequent disabling of the apparatus. It should exist only as an additional and independent precaution, which is very rarely called into action, and never in normal'working. The onlyproper normal method of regulation is that the rate of imparting heat to the circulating fluid shall instantly decrease when the temperature or pressure within it reaches a certain point. Various methods of securing this result maybe used,

andit matters not what particular method be chosen, and each maybe brought into action either by the temperature or by the pressure of the circulating fluid through appropriate thermostats, valves, or diaphragms. I confine myself to no particular method; but one or more attachments for this purpose are preferably used in all cases, and should come into action before the circulating pressures reach such a point as to open the circulation safetyvalve. This becomes especially important when the circulating fluid is water circulated under pressure to raise its boiling-point, as above described, and in most cases it is likely to be thus circulated under heavy pressures, if used at all, in order to get a large thermal head or a greater thermal range.

For the regulation of the maximum temperature of the circulating fluid three general methods are possible, which are independent of each other and may be effected by different means, and which,preferably, are all used. These are, first, regulation of the air-supply; second, regulation of the fuel-supply, and, third, waste of heat after combustion. These will be considered in order.

Regulation of air-supply.Inasmuch as the IIO circulating fluid can practically store no heat,

nor the boiler, either, when properly designed, as will be seen hereinafter, the main reliance for economical combustion must be on direct control of the rate of combustion through the air-supply or the fuel-supply, or preferably both.

The air-supply can be regulated automatically with great exactitude by making the heater perfectly air-tight, or as nearly so as may be, and providing two openings for airsupply, one of which admits air below the grate to support combustion and the other of which admits air above the grate in part to perfect combustion to the extent that the nature of the fuel makes necessary, but

chiefly to cheek combustion when necessary, by admitting air above the fire so as to destroy the draft through it, as well as to cool the gases of combustion. To this end the opening below the grate should be of such size as to admit all the air needed for good combustion at the most rapid rate when full open, an d no more. It should be controlled by any simple valve, preferably a plain flap'valve, which closes completely when the temperature or pressure of the circulation reaches a desired working maximum, and this should be the first regulatory adjunct to act. The opening or openings above the grate should also be controlled by some flap or other valve which never closes the opening completely if air above the fire is a necessity for good combustion, but which otherwise may be normally closed. Before heat begins to be wasted, as hereinafter described, however, this valve should open pretty widely, since it has the double effect of checking the production of heat, as well as getting rid of it wastefully, and thus is more economical.

Regulation of fucZ-su ppZ g .lVith any form of liquid, gaseous, or pulverized solid fuel this is very easily elfected by a valve acting concurrently with that controlling the airsupply for combustion. It should, therefore, in most cases be mechanically a part of the air-supply valve, and in all cases may and should be actuated by a common regulative connection, so as to be synchronous in its action. I contemplate the use of'such gaseous or pulverized fuel so far as possible, for the very reason that the supply is so easily regulated. When coal in solid form is used as fuel, such direct regulation is not possible but in practical effect it may be closely approached. I recommend in all cases that the grate be given an adjustable and automatic slow rocking or rotating motion, so that the fires may keep themselves in good order with a minimum of attention. It is far more important to do this than with the now usual processes of steam generation. These last are carried onunder such dangerous and unfavorable conditions at best that constant skilled attention is required anyway. My aim in developing this process has been to utilize to the fullest extent its inherent advantage of being naturally safe and self -regulative. Therefore Irecommend not onlythat this mechanical rotating or rocking action of the grate be always obtained, which may be done by a suitable connection from any moving part, but that it be made automatically variable according to the temperature or pressure of the circulating fluid, preferably by a connection with the same regulator which controls the air-supply, in such a manner that all grate motion ceases, or at least is diminished, whenever the circulating temperatures begin to rise above the desired maximum. It is easier to stop the motion altogether than merely to diminish it, since the first requires only some simple disconnecting device actuated by the thermostat or pressure device while the second requires a change of some leverage. Therefore instead of aiming at a continuous though variable movement the motion should for convenience be intermittent, but comparatively vigorous when it occurs. It should in any case be slow, however, in order to give its effect time to show in the temperatures before it goes too far. This regulatory adjunct becomes especially desirable when the fuel used is anthracite. In that case the base-burner principle, under which the fire is fed continuously by a magazine of fuel above it, will ordinarily give the best results, and if this be combined with regulated movement of the grate the fire may be kept for many hours together in just the condition required by the demand for heat, whether regular or irregular, without any further attention than to insure that the f uelmagazine is not exhausted.

lVaste of heat after combusiion.-There are four obvious efficient ways of effecting this end, all of which may be used, and which are preferably brought into action in the following order: First, opening a direct escape for the gases of combustion so that their heat is wasted; second, passing the circulating fluid through a wasteful cooler after it leaves the heater; third, a temperature safety-valve positivelyopened; fourth, a pressure safety-valve opened by excess of pressure. All these methods are wasteful, since they merely discharge to waste the excessive heat of combustion, which otherwise would be imparted to or remain in the circulating fluid. They should, therefore, not be the primary reliance for heat regulation any more than the safetyva-lve, though they may be made so by suflicient care in firing; but the regulative methods previously described, which are a check upon the actual generation of heat, are preferably used in all cases, whether with or without any or all of these wasteful methods. The opening of an escape for the gases of combustion may be secured by a damper of any common form actuated by any suitable means, such as a thermostat, and the temperature safety-valve may be placed in any suitable position upon the circulating system and operated by any similar means. Any common or suitable form of pressure safety-valve may be used.

The wasteful cooling of the circulating fluid after it leaves the heater may best be secured by an open evaporative tank, into which the circulating fluid is directed from the normal circulating system when the temperature rises too high, so that the temperature of the circulating fluid in the boiler may at once be reduced independently of any lessening of the amount of heat imparted thereto. This change of the circulation is preferably controlled automatically by means coming into effect before the safety-valves, but I after the other regulative means above stated, so as to act in case any of them should fail or all prove insufficient; but it is preferably controlled manually also, the special and most important function of this feature being to cut off at once the circulating fluid from the boiler when the boiler'system is thrown out of operation, and it is then desirable that this should be done by hand at once and independently of any other regulative appliance. In fact, deflecting the circulation into this wasteful cooler is one of the best ways of stopping the engine when there is no special haste to do so, since it has the further advantage of relieving the boiler and heater of all sudden increase of temperatures. This change of the circulation is indicated in Fig. 8, which shows in diagram the complete circulating system with two boilers and a condenser in circuit. Under the arrangement shown, engine E is a condensingengine working between the boilerB and condenser C, while E is or maybe a non-condensing engine discharging its exhaust into the atmosphere. So far as the circulating system is concerned, it is indiflerent whether E is non-condensing or whether it has a condenser not in circuit, served bysome external cooling agent. To make the circulating system of Fig. 8 conform to that of a single boiler, it is only necessary to omit boiler B and condenser C and their connections and run pipe V directly from the lower part of boiler B to the heater H.

The normal circulation is shown in Fig. 8 by the parts in full lines, and is from the heater H, through the pipe V, to the expansion-tank T, and thence through the secondpipe V to the boiler B. After circulating through this, as shown by dotted lines, the circulating fluid passes by the pipe V to and through the second boiler B, which may ordinarily contain some more volatile working substance than boiler B. In any case, the circulating fluid is considerably cooled by passing through the boiler B, and thus is fitted to return through a condenser O, which receives and condenses the exhaust-steam from the engine E, served by the boiler B, and to absorb and return to heater some fraction of the otherwise wasted heat of engine E. From the condenser O the circulating fluid returns through the pipe V to the heater H, to be reheated and repeat its circuit. The abnormal circulation is shown by the parts in dotted lines and is brought into action by shifting three-way cock as, when the boilers are cut out of the circulation and the circulating fluid passes from the tank T, through the pipe V and open evaporative tank Z, back to the heater. This abnormal circulation comes into action temporarily only for the brief periods in which withdrawal of heat through the boilers has ceased while there has not yet been time to stop the generation ofheat in the heater, so that the excess must be dissipated unless the internal temperatures of the system are to increase obj ectionably. WVhenever gaseous, liquid, or pulverized solid fuel is used, this abnormal circulating system becomes unnecessary, because in that case the generation of heatcan be stopped as suddenly as its withdrawal. There is another method by which this wasteful regulation may be attained viz., diverting the circulating fluid, or a part of it, from the heater, or from the hottest part of the heaterbut on account of obvious mechanical and economical difliculties, and especially the importance of protecting all parts of the heater against overheating, it will probably not be found desirable to use it.

It is obvious that many different means may be used for securing regulation of the maximum temperature by some or all of the methods above pointed out and that either thermostatic or pressure regulation may be used. As between thermostatic and pressure regulation, however, I prefer the former, since a thermostat may be made so simple, and yet so positive and certain in its action. Whichever be used, however, we may, by a single thermostat or regulator, control all the following regulative features so as to act at successive small increments of temperature or pressure: first, decrease the fuel supply or stop the grate-shaker; second, shut off air supply below grate; third, admit air above grate; fourth, discharge hot gases wastefully; fifth, divert the circulating fluid into an evaporative pan for wasting heat; sixth, open positively some relief-valve. It is better that the positive action of a proper thermostat should be relied on to open a safety-valve rather than internal pressure, because the thermostat acts or may act with practically resistless power, while it is almost impossible for it to get out of order. Nevertheless, as it is conceivable that it might fail, an independent pressure safety-valve of the usual type should be added. By these six methods, together with a pressure safety-valve, we may have perfect regulation of maximum temperatures, and at all times in the most economical way which is adequate for the needs of the moment. As they are all so simply attained, there is no motive for omitting any one of them. Nevertheless, as each one of them is independently effective, any one or more of them may be used without the others, and with a little more care and risk may be sufficiently effective and but little more wasteful.

Adjunct B.Regulation of Volume of Circulating Fluid. 1

The circulation may be effected in part by the natural action of the difference in gravity of hot and cold fluids, as outlined in Fig. 8, where the expansion-tank T is at the top of the system and the heater H at the bottom. By an old and well-known process it is only necessary that the expansion-tank shall thus be the highest .point on the system and the heater the lowest or nearly the lowest, to have quite a rapid natural circulation begin under the conditions sketched, and continue so long as heat is supplied in H and abstracted in some considerable quantities in B or else- Lil where on the circuit IIV TV 13V BV CV II. The rapidity of natural circulation may be increased by elevating the boilers and tank T, and this natural circulation alone may nearly or quite sufflee if the circulating-passages be made large enough; but for reasons given more fully below a high speed through small passages gives better evaporative duty than a low speed through large passages, and hencea circulating-pump is nearly always expedient even with only one boiler in circuit, and still more when there are several boilers and, perhaps, several condensers also. If the expansion-tank has only a moderate elevation, the circulation will be purely liquid only so long as the liquid in the tank T stands at or near to the level of the hot intake. Thereafter unless there be a circulating-pump and the engine is in motion it will only be continued by the generation of steam in the heater, which is objectionable because no metal surfaces exposed to the direct action of fire should be alternatelybare and in contact with liquid. Therefore it is desirable that the circulating fluid shall at all times be maintained in a nearly-constant volume, and this in starting the fires as well as when working, though this latter is not so important. Under these circumstances when a moderate range only is contemplated, as from zero to 100 centigrade or less, as in most hot-water heating-plants, it is suflicient to fill a smallsized tight drum about half full and rely on occasional inspection to maintain the proper height of liquid within it. The change in the volume of water for such a range is only about four per cent; but when temperatures as high as TOO centigrade (752 Fahrenheit) or more are contemplated the change in volume is greatly more than in proportion, being nearly one-third, and, moreover, most of the oils expand with heat about twice as much as water, so that a very great change of volume must then be provided for. This maybe done either by using a very large expansion-tank or by providing means for regulating with some exactitude the level of liquid within it. If the firstexpedient be resorted to, the tank should have for water an interior volume of about two-thirds of the total volume of the liquid circulation in order that there may be some liquid in the tank when it is coldest, and that it may not be more than half full when it is hottest. This is the simplest expedient, and in order that it may be feasible it is desirable that the volume of the circulating fluid should be kept at its minimum by using no unnecessary lengths or sizes of circulatingpassages; but the expansion-tank may be made much smaller and the volume of eirculating fluid kept constant regardless of temperature or oversight, which is highly desirable, by providing a separate storage-tank of ample eapaeity,which yet need not be great, at some convenient point, preferably higher than the expansion-tank, and connecting it therewith in such manner that when the expansion-tank is more than about half full liquid flows from it to the storage-tank, and when it is less than half full liquid flows into it from the storage-tank. This may best be effected by having inside the expansion-tan k a float of some considerable size and power, which floats about half immersed, so that it may act with about equal effect by its gravity downward or by its flotation upward. \Vhen the liquid falls toolow, this float opens a valve which equalizes steam-pressure between the expansion and storage tanks, and so permits liquid to flow by gravity or otherwise from the latter to the former through a pipe connection between the bottoms ofthe two tanks, which pipe should be provided with a checkvalve against any undesired return-current. After sufiieient liquid has thus been admitted the float will rise and close the valve, leaving the steam admitted to the storage-tank to condense therein by natural radiation, either producing a vacuum or restoring atmospheric pressure, as desired. If the liquid rises too high, it can only do so because it is expanding from heat, which means that there is or always may be, by having a trifling percentage of some more volatile ingredient in the circulating fluid, some small pressure,at least, in the expansion-tank. Therefore all that the float need do is to open a valve in the bottom, which closes a pipe leading to the storagetank, and the internal pressure will drive the surplus liquid out directly. Both of these valves may and should be quite small, since the changes of volume should take place quite slowly. Therefore the work thrown on the float is very light, so light that the float may be entirely dispensed with and the gravity of the contained liquid alone used to actuate the valves, by making them sufficiently delicate; but this would be inexpedient. Tem peratu res or pressures cannot be used to effect this regulation for obvious reasons; but the mechanical details may be greatly varied. I attach considerable importance to this rcgulative adjunct. To use the process in the best way we must deal with high-liquid temperatures, implying great changes of liquid volume. By the aid of this adjunct, nevertheless, we may use quite a small expansion-tank. "0 may be sure that it is just full enough and not too full under all conditions and without any manual regulation, and we may put the storage-tank at any distance we please from the expansion-tank, connecting the two by two small pipes, so that it will not be in the way. It is not even necessary, though it will usually be expedient, that the storage-tank shall be higher than the expansion -tank, since some slight and constant pressure may be substituted for'gravity.

Adjunct C'.--B0Zer Process.

A circulating fluid which is otherwise properly handled may be used with great advantage with any kind of boiler, as we have seen, since we may leave the boiler otherwise the same and get improved conditions for steam generation and a far greater steam-supplying capacity without other mechanical change than substituting a circulating fluid for fire as the heating agent. As above stated,however, the circulating fluid should be applied, first, to the hotter parts and then to the colder parts of the working substance, being passed downward from top to bottom of the pressuregencrator, instead of applying the heat first to the bottom of the working substance, as at present. The difference between the two cases and the proper functional management of the circulating fluid may be most clearly shown by taking a simple type of boiler originally designed for fire-say a vertical tubularthough it matters not what type be chosen and showing how such a boiler may best be adapted to the use of a circulating fluid. Expressed in the fewest possible words, the proper method is to enter the circulating fluid hot through the passage which before was the uptake or chimney, and then pass it downward through the tubes in which the gases before went upward, whence it goes much cooled into the fire-box which was before the source of heat, and thence out through the grate, thus directly reversing the usual currents and comparative temperatures. In every sort of boiler the circulating fluid should enter at the top, thence work its way down, more or less circuitously, and pass out cooled at the bottom. In the vertical tubular boiler this descent is direct through passages which already occupyboth the steam-space and the water-space. In a horizontal tubular boiler the descent is properly in horizontal zigzags, and there are no tubes in the steam-space, which should accordingly be added for the best results. In either case the need for circulation has vanished and the tendency to circulation has been largely reduced. The need for circulation resulted only from the intense heats of the fire and the generation of most of the steam at the bottom of the boiler. The tendency to circulation has been decreased, as the most of the steam is now generated near the top and none near the bottom, thus avoiding largely the mechanical action of the rising steam. Some tendency to circulation still remains, however, owing to the unequal distribution of heat in different parts of the boiler, which is increased largely by the side spaces left cold intentionally to provide passages for downward circulation. It is impor tant that all tendency to circulation be eliminated and circulation prevented, and I secure this result by the uniform distribution and close spacing of the heating-surfaces. By uniform distribution is meant such distribution of the heating-surfaces that all of the vertical columns into which the water in the boiler maybe conceived to be divided between such heating-surfaces and between the heating-surfaces and the boiler-shell shall receive substantially the same amount of heat and be of the same mean temperature and density and no cold spaces beleft for downward circulation, as in the boilers now in use. The distribution of the space between the heatingsurfaces and between the heatingsurfaces and boiler-shell will depend upon the nature and size of the heating-surfaces employed. If tubes be used and they are of the same size throughout the boiler, the spacing will be equal, but the spacing may and preferably should increase somewhat with the size of the tubes, if different-sized tubes be used. By

closely spaced is meant that the heatingsurfaces must be spaced at such distances apart as to avoid the formation of any cold interspaces through which downward circulation may be set up. If tubes be used, the requisite spacing will depend somewhat upon their size and the intensity of the heating action,the smaller the tubes and the lower the intensity the closer the spacing required. The effect of this construction is that the water is at differential temperatures and densities throughout in horizontal layers, lightest at the top and heaviest at the bottom, and therefore actively resists and prevents any circulation which the steam generation might otherwise cause. This being the case, it will be easily seen why any type of fire-boiler is needlessly bulky and clumsy for use with circulating fluids, and why the continued use of such types would involve great and needless sacrifice. In the first place, as we have no need to provide for circulation, and as our heatingsurfaces never rise above or fall below an externally-fixed temperature, we neither gain nor lose dynamically by having more liquid in the boiler than is needed to givethe desired area of liquid contact with our heatingsurfaces. As we gain a mechanical advantage by reducing the contained quantities we should do so. We need no large liquid mass to receive irregular heat impacts, because we have none. 7e need none to prevent excessive steam generation at particular points or moments, because our steam generation, if excessive, is continuously and uniformly so and not affected by interior volume, so that it must be controlled in other ways. As no interior circulation is wanted and none will occur, however widely spaced the tubes, within the limits defined we need no wide spacing of tubes. Therefore the tubes may be and preferably are very closely spaced whatever their size, and no more liquid than is needed to give contact with them need be inclosed. There is indeed one small advantage from having a large volume of contained liquid, that it serves in some degree as a reserve of power; but this end is better attained ordinarily by the thermostatic regulation of the fires. As economy requires that they be not pushed very hard in regular working, they will respond instantly and automatically to a considerable extra demand under the conditions of this process. A still more important end is or may be secured by the construction explained, which carries the =currents past each other, and so introduces differential temperatures within the chamberviz., that it reduces the necessary mean thermal head. This feature becomes of much importance in certain processes referred in other applications and is there more fully explained; but the tubes no longer need to be large or thick to let gases of combustion through freely or to resist temperature strains or abrasion of einders. Therefore they should be quite small, since the liquid at slow speed liows through small tubes equally well and the weight of the tubes per square foot of surface varies directly with the diameter and the heating area per cubic foot of boiler inversely therewith. Therefore we need twice as large and heavy a boiler with one-half-inch tubes as we do with onefourth inch, and proportionately for other diameters. \Vith two-inch tubes the boiler is increased eightfold over one-fourthdnch tubes. It is even then so small that the larger sizes may often be use fully employed, and perhaps longer experience will indicate that larger tubes than In ow favor are preferable; but so faras I yet know one-fourth-inch copper tubes are more suitable for any size of boilers than larger tubes. \Yith tubes of this size the boiler may be, as already stated, so small that it may more properly be considered as a mere enlargement of the feed-pipe in which water is turned into steam as it moves along by passing between evenly hot surfaces at a fixed rate, since as much as one-hundred horse-power of steampower may be continuously and economically produced per cubic foot of total boiler volume, shown more fully hereinafter among mechanical details. Nevertheless it will often be inexpedient to attempt such very high duty, for reasons explained at the close of the description of the next adjunet-D It follows from these facts that the boiler-surfaces need not be tubes at all. I do not confine myself to them. They may instead be a mass of thin fiat plates closely spaced and indented or corrugated, so as to keep their spacing against whichever fluid is under the greatest pressure, whether the circulating or the working sub stance. Such a boiler is fully described and claimed in another application, Serial No. 507,258, filed April 12, 189%. In any case the boiler will ordinarily give the best results when from two-thirds to four-fifths full of liquid, and it is better to have a considerable area of heating-surface, perhaps ten to fifteen per cent. of the whole,devoted to superheatin g uses alone. The possibility of very highly superheating without risk or any special appliances therefor is one of the greatest advantages of the use of my process.

As we have no need for any steam-space beyond what is required for generating and superheating the steam, it follows from all that has preceded that the best boiler for use with a circulating fluid will consist of a massof thin and delicate heating-surfaces filling steam space and waterspace alike without any distinction between. them, with no greater total bulk than is needed to insure enough heating-surface, with the circulating fluid entering hot at the top and working its way downward to the bottom, and with the working substance entering cold at the bottom and leaving hot at the top. Other details may be varied at pleasure within wide limits, as also the character of the heating-surfaces; but the character and arrangement of surfaces described will be found to secure many advantages.

The principle that heat applied to a vaporizing substance under pressure should always be most intense at the top and coldest at the bottom is one of general application, and the mere correction of this error, with a minimum of other change, will always result in improved funetional action, all the present commercial forms of boilers violating this principle. The broad basis for this principle lies in the fact that inasmuch. as all possible working substances expand with heat and contract with cold gravity always tends to segregate the exterior mass of working or heated substance into horizontal layers, coldest at the bottom and hottest at the top, and when the process of heating produces and includes a change from the liquid to the gaseous form this tendency to segregation is of coursevastly increased and becomes irresistible by any violence of circulation. Therefore, in order to produce the smoothest and most eilicient action of a boiler the heating agent, whatever it is, should act first at the top with its greatest intensity of heat and then pass from the top downward, or in a reverse (lirection,to the heated substance, which should enter cold at the bottom and leave hot at the top. The heating agent thus first superheats, then surrenders heat with great intensity and rapidity for vaporization, which confines that process chiefly to the immediate vicinity of the surface, its intensity decreasing directly with the depth below the surface untilat one-fifth to one-half of the total depth of liquid vaporization practically ceases. Only when the working substance is fed at the boiling-point will it extend through the entire depth, and then its intensity will decrease with the depth, so that three-fourths of it will occur in the upper half of the liquid. The heating agent having passed below this depth, all the remainder of the liquid is still below the boiling-point, and hence more efficient than it otherwise could be for abstracting heat from the now much-cooled heating agent, and hence the latter is cooled before it is discharged, sensibly, below the point possible, when, in most present types of boilers, most of the gases never encounter any liquid below the boiling point before discharge. Heat from whatever source and however communicated should always be supplied to a pressure-generator first and hottest at the top, and thence should be decreased in intensity ICC applying thisprinciple form in themselves parts of the invention, although they are preferably used in a system employing the other features of the invention. A boiler or pressure-generator designed according to these methods is a reversible mechanismthatis to say, it is onlynecessary to reverse the direction of the two currents of heating and heated substance which pass through, all temperatures and pressures remaining the same-and it becomes an equally efficient condenser or cooler of the vapor which before it generated. This results from the fact that the real aim in both cases is the samethat is,to transfer heat from one substance to another. Hence, for reasons already given,the substance which is to surrender heat should in each case enter at or near the top and go out at or near the bottom, while the substance which is to absorb heat should enter at or near the bottom and go out at or near the top. When the chamber is being worked as a boiler, the working substance is to absorb heat and enters as a liquid from the bottom, going out as a vapor at the top. hen the same chamber is to be worked as a condenser for the same vapor, the working substance is to surrender heat, and hence enters as steam at the top and goes out at the bottom. The heating agent in each case alike flows in the reverse direction to the working substance, its proper top and bottom temperatures remaining the same. Ordinarily the vapor which we wish to condense is not in quite the same status as the steam which we wish to generate, and some slight mechanical difference may result from this fact; but this is another issue and so small a one in all ordinary cases that a welldesigned boiler and condenser should be mere duplicates of each other, despite the differences of pressure.

My improved process of condensing or cooling a vapor depending upon the correct application of the principles above stated is of general application independently of the other features of the invention, and this process forms in itself a part of the invention, and it will be understood that an apparatus for transferring heat from one substance to another, constructed as described and claimed, forms a part of the invention, broadly considered, whether used for the purpose of generating vapor pressure or for condensing.

Adjunct D.-Regulatz on of Minimum Temperature of Circulating Fluid.

By this I mean the regulation of the temperature of the circulating fluid on the cold sidethat is, as it passes from the boiler, which is its minimum. This adjunct is indispensable in some of the more complex forms of the process, with several boilers in circuit working at different temperatures, and even in the simplest case with only one boiler in circuit it is always desirable. The best method of effecting this regulation is by a thermostat,

and the best method of applying the thermostat is to regulate with it the speed of circulation,'so that if the circulating fluid is leaving the boilers too hot its speed may be checked and if too cold its speed may be increased. The best method of doing this latter is to have a circulating-pump throwing some excess over the maximum demand for circulation and connected with this pump a thermostatically-controlled by-pass which permits a varying percentage of the liquid pumped to circulate round and round through the by-pass and pump without making the circuit through the heater and boiler or boilers. If the minimum temperature be not regulated, we shall not have a constant mean temperature within the boiler, even though we have a constant maximum, and we shall often have the circulating fluid returning to the heater so hot as to waste much heat.

It is possible to regulate the minimum temperature without controlling the speed of circulation. For instance, if there be a perfectly-uniform withdrawal of steam and supply of working substance circulating fluid which enters the boilers at a constant maximum will leave them at a constant minimum. we may also arrange to vary the proportion of the boiler-surface which is active by varying the area which is immersed in working substance; but this variation of extent of active surface is preferably a feature of the control of the quantity or pressure of steam generation, as explained later, when it is used at all.

The thermostat by which the speed or volume per minute of the circulation is regulated I term the cold thermostat. It should be sensitive and quick-acting, checking the circulation almost completely as soon as the circulation begins to run too hot, as it will as soon as withdrawal of steam is checked, and opening wide as soon as it begins to run a few degrees too cold. It should be adjustable, so that it may be set for any desired temperature.

When the withdrawal of steam from the boiler suddenly stops, even though the cold thermostat may promptly stop the circulation, the boiler-passages will be full of hot circulating fluid, which is hotter than the contained working substance by the amount of the transmission interval, which may in cases be as much as 100 centigrade, or even more. Hence, as soon as withdrawal of heat stops, the boiler temperatures and pressures will equalize with the circulating fluid, and there will be a quick rise of pressure. The precaution which is generally preferable against this quick and certain increase of pressure is not to use such high circulating temperatures and large transmission intervals as to produce a dangerous pressure even when steam withdrawal stopsas, for instance, one exceeding thirty to forty atmospheres, which welldesigned boilers of the type hereinbelow described may easily stand. On this account,

chiefly, it is not expedient to try to force a boiler up to its ultimate capacity, which seems to vary directly with the thermal head; but in cases it may seem necessary or expedient to do this or excessive temperature may result from some accident without intention. \Vhenevcr this is deemed possible, it makes regulatory adjunct E, described below, desirable.

\Vhencver a condenser is included as part of the engine process this regulatory adjunct may conveniently be omitted, because the working substance then works in closed cycle and a pump of whatever type keeps the condenser nearly or quite empty by pumping all working substance as fast as liquefied back into the boiler, thus maintaining it therein at what will be, except for possible carelessness, a sufficiently-constant level.

For the practical reason that pure feedwaters are scarce and impure ones would rapidly coat the thin and highly-active surfaces which I prefer for my boilers I contemplate nearly always using a condenser, whether or not any considerable vacuum is aimed at, and whether or not a supply of conden sing-water is available. To this end I have devised a type of evaporative condenser, hereinafter described, which requires no more water than would otherwise be required for feed-water, which is extremely compact, and which will readily give a considerable degree of vacuum, if desired, and at all times enable the feed-water to be used over and over, and thus to maintain a tolerably-constant water-level in the boiler. Vhen no condenser is thus connected with the boiler, however, it is highly important that the waterlevcl in the boilers should be regulated to the extent of insuring that it shall not rise above a certain level, because, should it do so, the boiler is of such small interior capacity, and so nearly full of liquid at best, that the irresistible force of liquid expansion may be called into action and the boiler ruptured. It may be so simply effected, moreover, that it may be better in all cases of importance to regulate the water-level directly, whether or not a condenser be used. Any one of a variety of well-known mechanical devices may be used to effectthis regulation. The proper one to select depends, primarily, on how the feed-pump is driven, whether directly from the engine, by a separate engine, by electricity, or by the direct action of steam. I prefer the latter method, and the regulating device which I deem best consists of nothing more in substance than a little ball-valve float,which when the water-level rises too high rises and closes the aperture through which steam escapes to work the pump, as fully described hereinafter.

Adjunct F.RcguZcu/i0n of the Degree (f Pressure that can Eris-i in the Boiler.

This adjunct may best be secured by a mere water safety -valve, through which, when the steam pressure reaches a certain excess above the desired working pressures, just before it reaches the pressure at which the steam safetyvalve is set to open, all liquid is blown. out of the boiler through the feed-pipe or other suitable connection. This liquid. may either be discharged to waste or blown back into the working-substance supply or into the condenser. The last is preferable, if there be a condenser. The pum if operated by direct action of steam, will then immediately begin to return the water to the boiler, but will not be able to do so in any quantity until the pressure falls below that at which the liquid blow-off opens, either because of cooling or of starting the engine. \Vhen the pressure thus falls, however, the boiler will then immediately begin to fill, and if provided with adequate pumping-power will fill up to the level at which the immersed surface will just suffice to generate steam at the rate at which it is being drawn oil? for the time being or to the level fixed by adjunct E.

The adjuncts above described relate particularly to the generation of the vapor-pressure. There are also certain useful results which may be secured by special applications of the circulating fluid, which make the complete process more economical. Among these the two followin are the most important, and in connection with features of the process above described form parts of the invention.

The circulating fluid is particularly suitable for jacketing the engine-cylinders as 110w usual with steam, and it is preferably thus applied when my improved process is used in connection with expansion-engines. Its chief advantages for this purpose are that it is or may be at a higher temperature than the steam, while not too high, and no provisions are required for taking care of the water of condensation, nor for making the steamjacket steam-tight, nor for making it capable of resisting pressure, except that of the circulating fluid when the latter is circulated un der pressure.

The circulating fluid, after having subserved its function of supplying heat to the working substance, may be used to condense the vapor of the working substance, and thus be partially heated before its return to the heater. Vith a single boiler there is no advantage in thus running the circulating fluid through a condenser, unless the circulating fluid be cooled between the boiler and eondenser, since it is not cooled enough in one boiler to absorb any otherwise waste heat on its way back to the heater; but if two boilers in circuit be used instead of one, the second one of which should or may use a more volatile working substance than the first, the circulating fluid will be cooled enough by the second boiler to be able to absorb some waste heat from the engine of the first boiler. In that case the circulating fluid would pass through a second boiler after the first, then through the cold thermostat,and then through a condenser interpolated in the cold circulation-pipe V, as outlined in Fig. 8. Of course the same advantage exists in using the circulating fluid for condensing if the fluid be.

cooled after leaving the first boiler by its use for any other purpose than for a second boiler.

Some of the betterments of the engine process proper or modes of using steam, which are made possible by the superior methods of steam generation so far described, are illustrated in Figs. 2 to 7, and may be thus described.

In the ordinary engine process the great thermal interval between the temperature of combustion and the boiling-point of water under pressure is unutilized. The heat supply is lowered in temperature through the whole of this interval without dynamic gain. Having our circulating fluid, however, heated to a considerably-higher point than we require for our engine a, Fig. 2, and yet at a regulated and approximately constant temperature, and having the power to work with low thermal heads from the construction of the boiler, it is obvious that we have in this difference of temperature T T, Fig. 2, a working interval in which we may, if we please, work one or more additional heat-engines, using water or any other liquid or gas as a working substance. In Fig. 3 is illustrated to a rude vertical scale of temperatures one way in which we may do this, and with much advantage, since four engines are in efi'ect run with no greater rejection of heat than otherwise results from the use of two. In this construction the engines a and a are alone worked under the usual conditions for high-pressure engines, receiving at each stroke a new supply of steam and exhausting it wastefully into the atmosphere. The engine a receives its heat directly from the circulating fluid in the same manner as engine a, but at a considerably-higher temperature and pressure and compounds or transmits its waste heat to CL. The fourth engine a receives its heat from the circulating fluid indeed, but in such manner as not to finally lower its temperature, the circulating fluid being returned into the heater one or more times after supplying heat to the boiler of a, so that its original temperature may be restored. There is thus left a sufficient ther mal interval for the engine a to work in and yet void the heat in its exhaust at such a high temperature that it may be used to do about half the work of heatingup the circulating fluid through an appropriate condenser, and hence the engine a may use any working substance in closed cycle, preferably one of higher boiling-point than water, so

that the working pressures due to its temperatures may not be excessive. These four engines may be arranged mechanically in any way desired, the sole necessary condition being that the circulating-passages of their boilers shall be connected in such manner that the circulating fluid shall follow the following path, starting from the heater: heater, boiler of a, back to heater to be reheated to original temperature, boiler of a, where circulating fluid loses heat, boiler of a, where it loses more heat, condenser of a, where the rejected heat of engine a is reabsorbed into the circulating fluid; heater, to be re heated-and repeat circuit.

In Fig. 4 is illustrated a still simpler way in which two engines may be run with a saving of about half the heat supply of one engine. The circulating fluid is assumed to have only half the volume or mass V per stroke in Fig.

4 that it has in Fig. 3, so that the same quantity of heat, which is that necessary to run the engine a, cools the circulating fluid through twice as great an altitude of temperature. The engine a, by circulating passages not indicated on the diagram, is supplied with heat from H at the temperature T without permitting the circulating fluid to be finally lowered in temperature thereby, which latter is eifected by returning the circulating fluid to the heater to be reheated to temperature T after supplying heat for the engine a. After being thus reheated, however, the circulating fluid supplies heat to the engine a and is thereby lowered in temperature to T, which is cold enough to permit the returning circulating fluid to absorb half or more of the exhaust of waste heat of the engine a by passing through its condenser on its way back to the heater, thus relieving the heater of this proportion of the work which would otherwise fall upon it,with corresponding economy. The two engines may have any desired relation to each other mechanically, as before. The sole requirement is that the circulatingpassages shall carry the circulating fluid in the cycle described and shown.

In Fig. 5, which is drawn immediately be low the single-engine diagram, Fig. 2, to facilitate comparison, is illustrated how, by substituting three engines for the single engine a, each working from a little lower maximum temperature than the preceding one, additional power may be attained under the identical thermal conditions of Fig. 2, with the sole exception that we avail ourselves better of the thermal range open for work by actually working through a greater portion of it, as indicated by the comparative hatched areas of Figs. 2 and 5. The hatched areas of Fig. 5 imply working the steam of the first two of its three engines through compound cylinders, whereas the hatched area of Fig. 2 implies only a single cylinder; but otherwise they are the same, the quantity of heat received and voided and the manner of doing so being essentially identical, except that the thermal heads are smaller in Fig. 5, andhence the boiler heating-surfaces must be correspondingly greater. \Vith the types of boilers hereinbefore and hereinafter described heating-surface is gained so cheaply and compactl y that this is no great matter.

Figs. 6 and 7 show how the amount of work shown in Figs. 3 and i may be increased in precisely the same way as that shown in Fig. 2 was increased to that shown in Fig. 5 by tripling the number of engines and boilers worked within an identical thermal range, so as to avail ourselves more completely of our whole thermal interval for work.

In Fig. 6 the cycle of the circulating fluid, the sole rigid condition for any desired mechanical arrangement, is as follows: heater, boiler of first engine a and back to heater, boiler of second engine a and back to heater, boiler of third engine a and back-to heater, boiler of first engine a", boiler of second engine a, boiler of third engine a, boiler of first engine a, boilcrof secondengine a, boiler of third engine a, condenser of third engine a, condenser of second engine a, condenser of third engine of, and back to heater to repeat the circuit.

Figs. 2 to 7 are designed to be merelyillustrative and not at all to give either the only methods or those of highest efficiency employing my improved engine process, some of which latter are made the subject of separate applications. On the contrary, the details of the primary process covered by this application may from its nature be varied almost indefinitely.

It will be understood by those skilled in the art to which the invention relates that the process above described maybe carried out by apparatus widely different in construction, arrangement, and mechanical detail, and the invention, considered broadly, is not to be limited to any particular form of the apparatus employed or of the devices forming parts thereof. In Figs. 9 to 18, however, I have shown, largely in diagram, a simple apparatus for carrying out the complete process, this apparatus and the special devices shown being well suited for the purpose, and the general combinations of this apparatus and certain specific features of the same form part of the invention covered by this application.

The most important features of the apparatus relate to the boilers or pressure-genea ators and the condensers or coolers, with their connections to the heater and the attach ments for performing the functions pointed out above, as desirable, it being understood that this apparatus may be used with any particular type of expansion heat-engine doing work through the expansion and consequent cooling of a confined working substance.

Externally the heater II maybe of any suitable construction, being preferably a plain iron box lined internally or externally, or both, with non-conducting matcrial,as usual in such constructions. The furnace,if for anthracite,

is preferably of the ordinary base-burner variety, as shown, provided with the lire-box A, fed from the central magazine I) and provided withthe rocking grate l). The cold circulating fluid enters at the base of the heater, passes upward through the coil of pipes V, about the vertical partition 0 to the top of the heater, thence downward outside the heater in the pipe V into the annular fire-pot chamber F, whence it passes upward through the inner vertical pipes V to the top annular or manifold G, and thence through the circulation-pipe V outside the heater, onward to the expansion-tank and boiler.

The air supply is regulated externally by any suitable damper to about the volume required for combustion; but there should be some excess of this supply, and to elfect a more accurate automatic regulation it is preferably subdivided, the air which supports combustion entering directly under the grate through passage I, and a portion, which serves to insure complete combustion and to dilute the gases of combustion and check the fire when desired, entering above the fire-pot through the passage 1, these passages being controlled, respectively, by flap-dampers (l cl. From the fire-pot the mixed air and products of combustion pass through the perforated shield c, and then are deflected out ward by the cone K between the pipes V, connecting the annulars or manifolds F G, thence passing upward over the partition 0, forming the inner furnace-chamber, and downward between and about the coil of pipes V, entering the flue L at the base of the furnace, whence they escape by the pipe L. In case the fires are giving out too much heat, however, as is assumed in Fig. 0, athermostatically-controlled damper f closes L and opens a direct connection M for the escape of the gases.

The maximum temperature of the circulating fluid, as above stated, is preferably regulated by a thermostat, which, together with the attachments by which this regulation is secured, maybe of any suitable form. I have shown, however, asimple thermostat, which will be found efficient, and this thermostat is preferably placed between the heater II and expansion-tank T, and in the form shown consists of a stout wooden rod T placed parallel with and adjacent to the circulating-pipe V, this portion of the pipe being formed, preferably, of a thick well-lagged brass or copper tube. As the wooden rod does not change in length with temperature, while the brass or copper tube expands largely and will be sensibly of the same temperature as the circulation, the relative length of the tube and rod gives a positive, simple, and powerful thermostat. \Vhile the circulating-pipe is shown as part of the thermostat, it will be understood that a tube may be added to form the thermostat, if desired, instead of using the circulating-pipe. For the purpose of transmitting the movements of the thermostat a lever N is pivoted upon the end of the rod T",

with its short arm connected to the pipe V at the end of the portion used for the thermostat, its long arm being connected by a chain to one end of a weighted lever g, connected by another chain 10 to a bell-crank lever h, from one end of which a connecting rod or rods 11 run to the dampers (Z d, and from the other end of which a connecting-rod 12 runs to the damper f. By these connections the damper d is closed and (1 opened when the temperature reaches the point for which these parts are set and the reverse as the temperature falls, and the damper f is actuated to open the passage M for the products of combustion when the temperature rises to a certain point and to close the passage M more or less as the temperature falls, the relative times of open ing and closing of the dampers d d f being adjusted as desired, as by lost-motion connections in case a single connection from the lever N is used, the rod 11 being shown as passing through a weighted arm on damper d and carrying a stop by which this arm is raised and the valve closed against the weight, which operates to open the damper as the temperature rises. The particular form of the connections may be varied to suit mechanical convenience. This thermostat also controls the grate-shaker by the connections shown in Fig. 17 ,the grate I) being actuated by a crankarm 13, connected by a link 14 to a crank-arm 15 on a crown-wheel i, which is mounted in a frame is, pivoted to a fixed part of the construction and connected either to the rod 11, or as shown for the sake of clearness, connected by an independent rod 16 to the weighted lever 9, so that the frame It will be raised by the weighted lever as the temperature falls, and will be lowered by its own weight when released by the lever as the temperature rises. The crown-wheel i, when in its upper position, engages with a worm Z, driven continuously by suitable connection with the engine or an independent motor. To prevent excessive wear on the wheel 5, which would be caused by the wheel being brought into contact with the worm Z gradually, some device is preferably provided by which the throwing of the wheel 1' into and out of contact with the worm Z shall be instantaneous. In the construction shown, a bent spring 9 is used, engaging the end of the frame k, the spring resisting and preventing the movement of the frame 7c in either direction until its resistance is overcome, when the frame moves quickly. An adj listing-screw gives means for regulating the resistance of the spring-catch 9.

A safety-valve 2, controlled by the temperature, is preferably used on the expansiontank T, and this safety valve is shown as actuated from the thermostat-lever N by the following connections: The valve t is normally closed by a weighted arm 47, through which passes a rod 48, connected to the lever N, the rod 48 being provided with a stop which engages the weighted arm 47 to raise and open the valve t at the proper time, the valve being closed by the weight when the arm is released as the temperature falls. This same rod 48 may operate also the three way-valve cc, controlling the change of circulation from the boiler to the evaporative tank Z, and is thus shown, the valve-stem 49 being weighted and the rod 48 passing through it and being provided with a stop which engages and actuates the arm at the proper time to open the valve and change the circulation from the pipe V to the pipe V the valve being shifted so as to close pipe V and open pipe V to the boiler again by the weight on stem 49 as the temperature falls. At the lower end of the pipe V a valve '3 is placed, which need only be a check-valve of any suitable form permitting liquid to pass freely downward, but not upward. It will be understood that all these various valves and dampers for regulating the maximum temperature and connections therewith to the thermostat may be of any suitable form, and that the constructions shown are selected only as a convenient way of illustrating means for securing the desired results.

In practice it will be found preferable in different cases to use single or independent connections from the thermostat for the various devices, depending upon the mechanical construction and arrangement adopted for the heater and other parts of the apparatus. The construction shown, therefore, is simply illustrative and largely diagrammatic.

It will be seen from the above description that this maximum temperature thermostat, as shown, effects the following ends, the order given being that in which the motions occur, starting as the heat increases, the position of the parts in the drawings being that at which the temperature has risen to a point where the regulating devices connected with the heater are brought into action, but before the shifting of the circulation or opening of the relief safety valve: first, regulation of the maximum temperature of the circulating fluid through the fuel-supply by disconnecting the grate-shaker; second, regulation of the maximum temperature of the circulating fluid through the air-supply by first closing the damper cl, controlling the air-inlet I below grate, and then opening damper d, controlling the air-inlet 1 above grate third, regulation of the maximum temperature of the circulating fluid by opening damper f, controlling passage M, so as to permit the hot gases to pass directly upward to the flue L, instead of taking the more circuitous downward course over the heating-surfaces formed by the coils of pipes V; fourth, regulation of the maximum temperature of the circulating fluid by diverting the circulating fluid into an evaporative tank; fifth, regulation of the maximum temperature of the circulating fluid by opening safety-valve positively.

To provide for the remote contingency that the heat shall become excessive after some or all of these regulative features have come into 

